Relationship of different left bundle branch pacing sites and clinical outcomes in patients with heart failure.

BACKGROUND

Left bundle branch pacing (LBBP) is a novel physiological pacing modality. However, whether it delivers comparable efficacy with different capture sites in patients with heart failure remains unclear.

OBJECTIVE

This study aimed to assess the association between different pacing sites and the response of LBBP.

METHODS

Forty-three consecutive patients with heart failure, referred for successful LBBP implantation, were prospectively recruited in this study. Patients were assigned to 3 subgroups according to the paced QRS complex morphology (left bundle branch trunk pacing [LBTP], left posterior fascicular pacing, or left anterior fascicular pacing groups). Echocardiograms and electrocardiograms were recorded and analyzed at baseline and 6-month follow-up.

RESULTS

The response rate was 95.0%, 88.2%, and 83.3% in LBTP, left posterior fascicular pacing, and left anterior fascicular pacing groups, respectively. All subgroups were efficient in narrowing the QRS complex (QRS complex narrowing: 38.1 ± 10.8 ms, 36.4 ± 12.6 ms, and 40.8 ± 10.8 ms) and improving cardiac function (LVEF improvement： 25.7% ± 8.1%, 15.3% ± 8.1%, and 18.8% ± 4.4%). Compared with left fascicular pacing, LBTP resulted in longer peak left ventricular activation time (76.5 ± 10.2 ms vs 82.3 ± 6.5 ms; P = .037) and shorter duration from intrinsicoid deflection in V1 or V2 to QRS end (128.0 ± 6.0 ms vs 113.3 ± 5.2 ms; P＜.0001), along with better improvement in septal systolic longitudinal strain (P = .007) and lateral-septal myocardial loading inhomogeneity (P = .036). Linear regression analysis further revealed that left bundle branch capture sites were strongly associated with the improvement in peak strain dispersion (model R2 = 0.586; P = .042) and LVEF (model R2 = 0.425; P < .0001).

CONCLUSION

Different left bundle branch capture sites led to a subtle difference in mechanical synchrony, which may, in turn, affect LVEF improvement in patients with heart failure.